In the prior art lens barrel with a lock mechanism where the lens barrel includes several groups of lenses, an embodiment of the same has a feature that is a lens frame capable of fixedly holding at least one of the opposed endmost groups of lenses with fixing means applying force along the optical axis of the lens barrel while leaving the group of lenses adjustable in planes orthogonal to the optical axis (see Patent Document 1 listed below).
This arrangement has, as shown in FIG. 9, a lens frame 512 located at the endmost portion relative to the whole lens barrel when a group of lens 511 held in the lens holder 512 are used to adjust optics in the manner of parallel and eccentric adjustment. Hence, adjusting components can be set up in some simple way, and additionally, in practice, the operator is able to continually watch the lens frame 512 for more accurate parallel and eccentric adjustment of the optics through the lens frame 512.
Furthermore, a junction of the lens frame 512 with the focusing fixed lens barrel 514 is secured by fastening elements 517, with elastic elements 516 intervening therebetween, in a plurality of positions of bores in the orthogonal plane to the optical axis of the fixed barrel 514. In this way, the fastening elements 517 temporarily fitting those parts on each other cause the elastic element 516 to develop a constant load in the directions along the optical axis, and this obviates the effect of the gravity applied to the lens frame 512 to attain an accurate adjustment with an arbitrary amount of rectification.
After completing the adjustment, the fastening elements 517 are perpetually tightened till they keep themselves fixed in positions where resilience of the elastic element 516 no longer affects them, and thus, the lens frame 512 can be rigidly fixed relative to the focusing fixed lens barrel 514.
Another embodiment of the prior art lens barrel with a lock mechanism is that which eliminates a restriction on a rotation angle of a focusing ring but restricts a displacement of the focusing lens and associated elements for a unit rotation angle of the focusing ring to not so large an amount and which facilitates the focusing and is, after the focusing, capable of screwing lock screws down without causing defocus (e.g., see Patent Document 2).
A lens barrel 610 includes, as shown in FIG. 10, a fixed barrel 612, a focusing ring 614, and a focusing lens frame 616. A first cam groove 630 is defined inside the focusing ring 614. A first linear stud 632 is fixed to the focusing lens frame 616. A first longitudinal groove 634 is defined in the fixed barrel 612. A lock plate fastening pin (not shown) is used to fix a lock plate 670 to the focusing ring 614. When a lock screw 662 is screwed down, a tip 662b of the screw stalk forces the lock plate 670 to move till the lock plate 670 comes in contact with the outer surface of the fixed barrel 612.